From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
This patch implements handle preemption timer fastpath, after timer fire
due to VMX-preemption timer counts down to zero, handle it as soon as
possible and vmentry immediately without checking various kvm stuff when
possible.
Testing on SKX Server.
cyclictest in guest(w/o mwait exposed, adaptive advance lapic timer is default -1):
5540.5ns -> 4602ns 17%
kvm-unit-test/vmexit.flat:
w/o avanced timer:
tscdeadline_immed: 3028.5 -> 2494.75 17.6%
tscdeadline: 5765.7 -> 5285 8.3%
w/ adaptive advance timer default -1:
tscdeadline_immed: 3123.75 -> 2583 17.3%
tscdeadline: 4663.75 -> 4537 2.7%
Tested-by: Haiwei Li <lihaiwei@xxxxxxxxxxx>
Cc: Haiwei Li <lihaiwei@xxxxxxxxxxx>
Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
---
arch/x86/kvm/vmx/vmx.c | 23 +++++++++++++++++++++--
1 file changed, 21 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index bb5c4f1..7dcc99f 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5556,17 +5556,34 @@ static int handle_pml_full(struct kvm_vcpu *vcpu)
return 1;
}
-static int handle_preemption_timer(struct kvm_vcpu *vcpu)
+static int __handle_preemption_timer(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
if (!vmx->req_immediate_exit &&
- !unlikely(vmx->loaded_vmcs->hv_timer_soft_disabled))
+ !unlikely(vmx->loaded_vmcs->hv_timer_soft_disabled)) {
kvm_lapic_expired_hv_timer(vcpu);
+ return 1;
+ }
+ return 0;
+}
+
+static int handle_preemption_timer(struct kvm_vcpu *vcpu)
+{
+ __handle_preemption_timer(vcpu);
return 1;
}
+static fastpath_t handle_fastpath_preemption_timer(struct kvm_vcpu *vcpu)
+{
+ if (__handle_preemption_timer(vcpu)) {
+ trace_kvm_exit(EXIT_REASON_PREEMPTION_TIMER, vcpu, KVM_ISA_VMX);
+ return EXIT_FASTPATH_REENTER_GUEST;
+ }
+ return EXIT_FASTPATH_NONE;
+}
+
/*
* When nested=0, all VMX instruction VM Exits filter here. The handlers
* are overwritten by nested_vmx_setup() when nested=1.
@@ -6590,6 +6607,8 @@ static fastpath_t vmx_exit_handlers_fastpath(struct kvm_vcpu *vcpu)
switch (to_vmx(vcpu)->exit_reason) {
case EXIT_REASON_MSR_WRITE:
return handle_fastpath_set_msr_irqoff(vcpu);
+ case EXIT_REASON_PREEMPTION_TIMER:
+ return handle_fastpath_preemption_timer(vcpu);
default:
return EXIT_FASTPATH_NONE;
}
--
2.7.4
